Two types of phonological dyslexia – A contemporary review

Progressive verbal apraxia of reading

We identified a syndrome characterized by a relatively isolated progressive impairment of reading words that the patient was able to understand and repeat but without other components of speech apraxia. This cluster of symptoms fits a new syndrome designated Progressive Verbal Apraxia of Reading. A right-handed man (AB) came with a 2.5-year history of increasing difficulties in reading aloud. He was evaluated twice, 2 years apart, using multimodal neuroimaging techniques and quantitative neurolinguistic assessment. In the laboratory, reading difficulties arose in the context of intact visual and auditory word recognition as well as intact ability to understand and repeat words he was unable to read aloud. The unique feature was the absence of dysarthria or speech apraxia in tasks other than reading. Initial imaging did not reveal statistically significant atrophy. Structural magnetic resonance and FDG-PET imaging at the second assessment revealed atrophy and hypometabolism in the right posterior cerebellum, in areas shown to be part of his language network by task-based functional neuroimaging at initial assessment. This syndromic cluster can be designated Progressive Verbal Apraxia of Reading, an entity that has not been reported previously to the best of our knowledge. We hypothesize a selective disconnection of the visual word recognition system from the otherwise intact articulatory apparatus, a disconnection that appears to reflect the disruption of multisynaptic cerebello-cortical circuits.

Semantic network activation facilitates oral word reading in chronic aphasia

People with aphasia often show partial impairments on a given task. This trial-to-trial variability offers a potential window into understanding how damaged language networks function. We test the hypothesis that successful word reading in participants with phonological system damage reflects semantic system recruitment. Residual semantic and phonological networks were defined with fMRI in 21 stroke participants with phonological damage using semantic- and rhyme-matching tasks. Participants performed an oral word reading task, and activation was compared between correct and incorrect trials within the semantic and phonological networks. The results showed a significant interaction between hemisphere, network activation, and reading success. Activation in the left hemisphere semantic network was higher when participants successfully read words. Residual phonological regions showed no difference in activation between correct and incorrect trials on the word reading task. The results provide evidence that semantic processing supports successful phonological retrieval in participants with phonological impairment.

A case of acquired phonological dyslexia with selective impairment of Kanji: analysis of reading impairment mechanism using cognitive neuropsychological models for reading

We report a Japanese-speaking patient who showed acquired phonological dyslexia only in Kanji; difficulty in reading two-character Kanji nonwords despite her ability to read Kana nonwords, Kana words, and two-character Kanji inconsistent-atypical words; and inability to repeat reversal nonwords. We investigated the mechanism of nonword reading impairment using the dual-route cascaded model, it was likely that the reading deficit of Kanji nonwords with multiple pronunciations resulted from the dysfunction of the character-to-sound conversion rule system. The patient's reading performance on the dissociation of Kana and Kanji was considered to reflect the difference in the consistency of orthography-to-phonology mapping.

Two types of phonological reading impairment in stroke aphasia

Alexia is common in the context of aphasia. It is widely agreed that damage to phonological and semantic systems not specific to reading causes co-morbid alexia and aphasia. Studies of alexia to date have only examined phonology and semantics as singular processes or axes of impairment, typically in the context of stereotyped alexia syndromes. However, phonology, in particular, is known to rely on subprocesses, including sensory-phonological processing, motor-phonological processing, and sensory-motor integration. Moreover, many people with stroke aphasia demonstrate mild or mixed patterns of reading impairment that do not fit neatly with one syndrome. This cross-sectional study tested whether the hallmark symptom of phonological reading impairment, the lexicality effect, emerges from damage to a specific subprocess of phonology in stroke patients not selected for alexia syndromes. Participants were 30 subjects with left-hemispheric stroke and 37 age- and education-matched controls. A logistic mixed-effects model tested whether post-stroke impairments in sensory phonology, motor phonology, or sensory-motor integration modulated the effect of item lexicality on patient accuracy in reading aloud. Support vector regression voxel-based lesion-symptom mapping localized brain regions necessary for reading and non-orthographic phonological processing. Additionally, a novel support vector regression structural connectome-symptom mapping method identified the contribution of both lesioned and spared but disconnected, brain regions to reading accuracy and non-orthographic phonological processing. Specifically, we derived whole-brain structural connectomes using constrained spherical deconvolution-based probabilistic tractography and identified lesioned connections based on comparisons between patients and controls. Logistic mixed-effects regression revealed that only greater motor-phonological impairment related to lower accuracy reading aloud pseudowords versus words. Impaired sensory-motor integration was related to lower overall accuracy in reading aloud. No relationship was identified between sensory-phonological impairment and reading accuracy. Voxel-based and structural connectome lesion-symptom mapping revealed that lesioned and disconnected left ventral precentral gyrus related to both greater motor-phonological impairment and lower sublexical reading accuracy. In contrast, lesioned and disconnected left temporoparietal cortex is related to both impaired sensory-motor integration and reduced overall reading accuracy. These results clarify that at least two dissociable phonological processes contribute to the pattern of reading impairment in aphasia. First, impaired sensory-motor integration, caused by lesions disrupting the left temporoparietal cortex and its structural connections, non-selectively reduces accuracy in reading aloud. Second, impaired motor-phonological processing, caused at least partially by lesions disrupting left ventral premotor cortex and structural connections, selectively reduces sublexical reading accuracy. These results motivate a revised cognitive model of reading aloud that incorporates a sensory-motor phonological circuit.

Poor reading is characterized by a more connected network with wrong hubs

Using graph theory, we examined topological organization of the language network in Chinese children with poor reading during an auditory rhyming task and a visual spelling task, compared to reading-matched controls and age-matched controls. First, poor readers (PR) showed reduced clustering coefficient in the left inferior frontal gyrus (IFG) and higher nodal efficiency in the bilateral superior temporal gyri (STG) during the visual task, indicating a less functionally specialized cluster around the left IFG and stronger functional links between bilateral STGs and other regions. Furthermore, PR adopted additional right-hemispheric hubs in both tasks, which may explain increased global efficiency across both tasks and lower normalized characteristic shortest path length in the visual task for the PR. These results underscore deficits in the left IFG during visual word processing and conform previous findings about compensation in the right hemisphere in children with poor reading.

Aphasia and acquired reading impairments: What are the high-tech alternatives to compensate for reading deficits?

BACKGROUND

People with aphasia (PWA) frequently present impairments in reading comprehension. Such impairments can be particularly debilitating due to the limitations and constraints they impose on everyday life. Recent technological advancements in the field of information and communication technologies offer many compensative tools for PWA. However, most technological tools are designed for patients with speech production impairments. Instruments addressing reading impairments associated with aphasia remain scarce and underrepresented in the scientific literature.

AIMS

To conduct a state-of-the-art review of the technologies currently available to PWA and acquired reading impairments. In particular, this review covers (1) research on technologies explicitly developed to compensate for reading difficulties associated with aphasia; and (2) research into which accessibility features included in mainstream high-tech systems are helpful for PWA when trying to access written material.

METHODS & PROCEDURES

Following the Preferred Reporting Items for Systematic Reviews and Meta-Analyses (PRISMA) international standard, the authors conducted a systematic review from 2009 to 2019. The databases inspected were Scopus, Web of Science, PubMed, the Cochrane collection, IEEE Xplore, ScienceDirect and SpringerLink. Other research papers were included after checking the references of the selected papers.

MAIN CONTRIBUTION

The review reveals that research on compensative devices for reading impairments largely neglects tools for individuals with aphasia and acquired reading difficulties. Most of the studies in this field are qualitative investigations of how patients with literacy difficulties tackle everyday tasks with the help of mainstream technology (e.g., smartphone applications). Therefore, this paper highlights the scarce high-tech alternatives that support text comprehension in PWA and acquired reading impairments, and suggests further work on the development of customized software for smartphones and personal computers.

CONCLUSIONS

High-tech reading tools may help PWA to regain reading autonomy. PWA and acquired reading impairments employ a wide array of devices to overcome reading difficulties, which underlines the importance of reading in everyday life. However, the supports currently available are not yet flexible and accurate enough to answer their day-to-day needs. Thus, further work is necessary to enhance the compensative devices available to them. For instance, existing new technologies in the area of natural language processing (such as automatic text simplification) could potentially be used in compensative devices. What this paper adds What is already known on the subject Most research on high-tech compensative reading tools is focused on investigating how patients with aphasia and acquired reading impairments cope with their reading difficulties in everyday life by resorting to different types of technology. Yet, we still lack specific research on compensative reading technology for PWA. What this paper adds to existing knowledge This review shows that PWA with acquired reading impairments are offered limited options for accessing written content easily and autonomously-and those few resources that are available are not specifically designed for PWA. What are the potential or actual clinical implications of this work? Both aphasia and acquired reading impairments can vary in terms of both their severity and the associated typology of cognitive impairments. Therefore, it might be interesting to investigate flexible and highly adaptable reading support designed for them-and innovations in the field of information and communication technology might prove particularly fruitful.

Technology-Enhanced Reading Therapy for People With Aphasia: Findings From a Quasirandomized Waitlist Controlled Study

Purpose This study investigated the effects of technology-enhanced reading therapy for people with reading impairments, using mainstream assistive reading technologies alongside reading strategies. Method The study used a quasirandomized waitlist controlled design. Twenty-one people with reading impairments following stroke were randomly assigned to receive 14 hr of therapy immediately or after a 6-week delay. During therapy, participants were trained to use assistive reading technology that offered a range of features to support reading comprehension. They developed skills in using the technology independently and in applying the technology to their personal reading goals. The primary outcome measure assessed reading comprehension, using Gray Oral Reading Test-Fourth Edition (GORT-4). Secondary measures were as follows: Reading Comprehension Battery for Aphasia-Second Edition, Reading Confidence and Emotions Questionnaire, Communication Activities of Daily Living-Second Edition, Visual Analog Mood Scales, and Assessment of Living With Aphasia. Matched texts were used with the GORT-4 to compare technology-assisted and unassisted reading comprehension. Mixed analyses of variance explored change between T1 and T2, when the immediate group had received therapy but the delayed group had not, thus serving as untreated controls. Pretherapy, posttherapy, and follow-up scores on the measures were also examined for all participants. Results GORT-4 results indicated that the immediately treated group improved significantly in technology-assisted reading following therapy, but not in unassisted reading. However, the data were not normally distributed, and secondary nonparametric analysis was not significant. The control group was unstable over the baseline, improving significantly in unassisted reading. The whole-group analysis showed significant gains in assisted (but not unassisted) reading after therapy that were maintained at follow-up. The Reading Confidence and Emotions Questionnaire results improved significantly following therapy, with good maintenance of change. Results on all other secondary measures were not significant. Conclusions Technology-assisted reading comprehension improved following the intervention, with treatment compensating for, rather than remediating, the reading impairment. Participants' confidence and emotions associated with reading also improved. Gains were achieved after 14 therapy sessions, using assistive technologies that are widely available and relatively affordable, meaning that this approach could be implemented in clinical practice.

Mapping the intersection of language and reading: the neural bases of the primary systems hypothesis

The primary systems framework has been used to relate behavioural performance across many different language activities to the status of core underpinning domain-general cognitive systems. This study provided the first quantitative investigation of this account at both behavioural and neural levels in a group of patients with chronic post-stroke aphasia. Principal components analysis was used to distil orthogonal measures of phonological and semantic processing, which were then related to reading performance and the underlying lesion distributions using voxel-based correlational methodology. Concrete word reading involved both a ventral semantic pathway, and inferior and anterior aspects of the dorsal phonological pathway. Abstract word reading overlapped with the ventral semantic pathway but also drew more extensively on the superior and posterior aspects of the dorsal phonological pathway. Nonword reading was related to phonological processing along the dorsal pathway and was also supported by a more superior set of regions previously associated with speech motor output. The use of continuous measures of behavioural performance and neural integrity allowed us to elucidate for the first time both the lesion and behavioural correlates for the semantic and phonological components of the primary systems hypothesis and to extend these by identifying the importance of an additional dorsal speech motor output system. These results provide a target for future neuroanatomically constrained computational models of reading.

Reading and visual word recognition ability in semantic dementia is not predicted by semantic performance

This paper describes longitudinal testing of two Semantic Dementia (SD) cases. It is common for patients with SD to present with deficits in reading aloud irregular words (i.e. surface dyslexia), and in lexical decision. Theorists from the connectionist tradition (e.g. Woollams et al., 2007) argue that in SD cases with concurrent surface dyslexia, the deterioration of irregular word reading and recognition performance is related to the extent of the deterioration of the semantic system. The Dual Route Cascaded model (DRC; Coltheart et al., 2001) makes no such prediction. We examined this issue using a battery of cognitive tests and two structural scans undertaken at different points in each cases time course. Across both cases, our behavioural testing found little evidence of a key putative link between semantic impairment and the decline of irregular word reading or lexical decision. In addition, our neuroimaging analyses suggested that it may be the emergence of atrophy to key neural regions both inside and outside the anterior temporal lobes that may best capture the emergence of impairments of irregular word reading, and implicated inferior temporal cortex in surface dyslexia.

The Visual Word Form Area remains in the dominant hemisphere for language in late-onset left occipital lobe epilepsies: A postsurgery analysis of two cases

Automatic recognition of words from letter strings is a critical processing step in reading that is lateralized to the left-hemisphere middle fusiform gyrus in the so-called Visual Word Form Area (VWFA). Surgical lesions in this location can lead to irreversible alexia. Very early left hemispheric lesions can lead to transfer of the VWFA to the nondominant hemisphere, but it is currently unknown if this capability is preserved in epilepsies developing after reading acquisition. In this study, we aimed to determine the lateralization of the VWFA in late-onset left inferior occipital lobe epilepsies and also the effect of surgical disconnection from the adjacent secondary visual areas. Two patients with focal epilepsies with onset near the VWFA underwent to surgery for epilepsy, with sparing of this area. Neuropsychology evaluations were performed before and after surgery, as well as quantitative evaluation of the speed of word reading. Comparison of the surgical localization of the lesion, with the BOLD activation associated with the contrast of words-strings, was performed, as well as a study of the associated main white fiber pathways using diffusion-weighted imaging. Neither of the patients developed alexia after surgery (similar word reading speed before and after surgery) despite the fact that the inferior occipital surgical lesions reached the neighborhood (less than 1cm) of the VWFA. Surgeries partly disconnected the VWFA from left secondary visual areas, suggesting that pathways connecting to the posterior visual ventral stream were severely affected but did not induce alexia. The anterior and superior limits of the resection suggest that the critical connection between the VWFA and the Wernicke's Angular Gyrus cortex was not affected, which is supported by the detection of this tract with probabilistic tractography. Left occipital lobe epilepsies developing after reading acquisition did not produce atypical localizations of the VWFA, even with foci in the close neighborhood. Surgery for occipital lobe epilepsy should take this into consideration, as well as the fact that disconnection from the left secondary visual areas may not produce alexia.

The level of audiovisual print-speech integration deficits in dyslexia

The classical phonological deficit account of dyslexia is increasingly linked to impairments in grapho-phonological conversion, and to dysfunctions in superior temporal regions associated with audiovisual integration. The present study investigates mechanisms of audiovisual integration in typical and impaired readers at the critical developmental stage of adolescence. Congruent and incongruent audiovisual as well as unimodal (visual only and auditory only) material was presented. Audiovisual presentations were single letters and three-letter (consonant-vowel-consonant) stimuli accompanied by matching or mismatching speech sounds. Three-letter stimuli exhibited fast phonetic transitions as in real-life language processing and reading. Congruency effects, i.e. different brain responses to congruent and incongruent stimuli were taken as an indicator of audiovisual integration at a phonetic level (grapho-phonological conversion). Comparisons of unimodal and audiovisual stimuli revealed basic, more sensory aspects of audiovisual integration. By means of these two criteria of audiovisual integration, the generalizability of audiovisual deficits in dyslexia was tested. Moreover, it was expected that the more naturalistic three-letter stimuli are superior to single letters in revealing group differences. Electrophysiological and hemodynamic (EEG and fMRI) data were acquired simultaneously in a simple target detection task. Applying the same statistical models to event-related EEG potentials and fMRI responses allowed comparing the effects detected by the two techniques at a descriptive level. Group differences in congruency effects (congruent against incongruent) were observed in regions involved in grapho-phonological processing, including the left inferior frontal and angular gyri and the inferotemporal cortex. Importantly, such differences also emerged in superior temporal key regions. Three-letter stimuli revealed stronger group differences than single letters. No significant differences in basic measures of audiovisual integration emerged. Convergence of hemodynamic and electrophysiological signals appeared to be limited and mainly occurred for highly significant and large effects in visual cortices. The findings suggest efficient superior temporal tuning to audiovisual congruency in controls. In impaired readers, however, grapho-phonological conversion is effortful and inefficient, although basic audiovisual mechanisms seem intact. This unprecedented demonstration of audiovisual deficits in adolescent dyslexics provides critical evidence that the phonological deficit might be explained by impaired audiovisual integration at a phonetic level, especially for naturalistic and word-like stimulation.

Learning disabilities: definitions, epidemiology, diagnosis, and intervention strategies

Learning problems occur in about 5% of school-aged children. Learning disabilities are specific and life-long but present with different school problems at different ages, depending on such factors as age, medical history, family history, and intelligence quotient. Proper individualized diagnosis and treatment plans are necessary to remediate these problems and to offer adequate coping strategies. Many children who have learning problems can be classified into one of two major categories: the dyslexia group or the nonverbal learning disability group. The role of the medical professional is important to guide parents in the diagnostic and therapeutic process.

Longitudinal assessment of language and memory impairments in pathologically confirmed cortico-basal ganglionic degeneration

We report a longitudinal case study (patient EP) of histologically confirmed cortico-basal ganglionic degeneration (CBD) who presented with non-fluent progressive aphasia (NFPA). While NFPA has been documented in clinical descriptions of other reports of CBD, details are often limited and the majority of studies are cross-sectional in nature. The present study conducted detailed longitudinal assessment with EP over a period of two years that revealed substantial impairments of episodic memory, semantic memory, naming and particular aspects of reading and spelling. Our investigations identify key features of EP's pattern of impairment that warrant further examination with other cases of CBD. In particular, testing of EP's nonword reading and spelling found that both were impaired and declined over time. In addition, verbal recognition deteriorated faster than non-verbal recognition through the course of the disease. Our review of the literature suggests that poor nonword reading and spelling may be consistent features of CBD, but more studies are needed to confirm this suggestion, and to determine whether they warrant inclusion in profiling CBD.